author = "Klipp, Telmo dos Santos and Petry, Adriano and Souza, Jonas 
                         Rodrigues de and Paula, Eurico Rodrigues de and Falc{\~a}o, 
                         Gabriel Sandim and Campos Velho, Haroldo Fraga de",
          affiliation = "{Instituto Nacional de Pesquisas Espaciais (INPE)} and {Instituto 
                         Nacional de Pesquisas Espaciais (INPE)} and {Instituto Nacional de 
                         Pesquisas Espaciais (INPE)} and {Instituto Nacional de Pesquisas 
                         Espaciais (INPE)} and {Instituto Nacional de Pesquisas Espaciais 
                         (INPE)} and {Instituto Nacional de Pesquisas Espaciais (INPE)}",
                title = "Ionosonde total electron content evaluation using International 
                         Global Navigation Satellite System Service data",
              journal = "Annales Geophysicae",
                 year = "2020",
               volume = "38",
               number = "2",
                pages = "347--357",
                month = "mar.",
             abstract = "In this work, a period of 2 years (2016-2017) of ionospheric total 
                         electron content (ITEC) from ionosondes operating in Brazil is 
                         compared to the International GNSS (Global Navigation Satellite 
                         System) Service (IGS) vertical total electron content (vTEC) data. 
                         Sounding instruments from the National Institute for Space 
                         Research (INPE) provided the ionograms used, which were filtered 
                         based on confidence score (CS) and C-Level flag evaluation. 
                         Differences between vTEC from IGS maps and ionosonde IBC were 
                         accumulated in terms of root mean squared error (RMSE). As 
                         expected, we noticed that the ITEC values provided by ionosondes 
                         are systematically underestimated, which is attributed to a 
                         limitation in the electron density modeling for the ionogram 
                         topside that considers a fixed scale height, which makes density 
                         values decay too rapidly above similar to 800 km, while IGS takes 
                         in account electron density from GNSS stations up to the satellite 
                         network orbits. The topside density profiles covering the 
                         plasmasphere were re-modeled using two different approaches: an 
                         optimization of the adapted alpha-Chapman exponential decay that 
                         includes a transition function between the F2 layer and 
                         plasmasphere and a corrected version of the NeQuick topside 
                         formulation. The electron density integration height was extended 
                         to 20 000 km to compute TEC. Chapman parameters for the F2 layer 
                         were extracted from each ionogram, and the plasmaspheric scale 
                         height was set to 10 000 km. A criterion to optimize the 
                         proportionality coefficient used to calculate the plasmaspheric 
                         basis density was introduced in this work. The NeQuick variable 
                         scale height was calculated using empirical parameters determined 
                         with data from Swarm satellites. The mean RMSE for the whole 
                         period using adapted alpha-Chapman optimization reached a minimum 
                         of 5.32 TECU, that is, 23 % lower than initial ITEC errors, while 
                         for the NeQuick topside formulation the error was reduced by 27 
                  doi = "10.5194/angeo-38-347-2020",
                  url = "http://dx.doi.org/10.5194/angeo-38-347-2020",
                 issn = "0992-7689",
             language = "en",
        urlaccessdate = "14 abr. 2021"